linux-kernel - Re: [PATCH v3 1/9] LSM: Identify modules by more than name

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Date:   Mon, 28 Nov 2022 08:51:47 +0100
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Paul Moore <paul@...l-moore.com>
Cc:     Mickaël Salaün <mic@...ikod.net>,
        Casey Schaufler <casey@...aufler-ca.com>,
        casey.schaufler@...el.com, linux-security-module@...r.kernel.org,
        jmorris@...ei.org, keescook@...omium.org,
        john.johansen@...onical.com, penguin-kernel@...ove.sakura.ne.jp,
        stephen.smalley.work@...il.com, linux-kernel@...r.kernel.org,
        linux-api@...r.kernel.org
Subject: Re: [PATCH v3 1/9] LSM: Identify modules by more than name

On Sun, Nov 27, 2022 at 10:48:53PM -0500, Paul Moore wrote:
> On Fri, Nov 25, 2022 at 11:19 AM Mickaël Salaün <mic@...ikod.net> wrote:
> > On 24/11/2022 06:40, Greg KH wrote:
> > > On Wed, Nov 23, 2022 at 12:15:44PM -0800, Casey Schaufler wrote:
> > >> Create a struct lsm_id to contain identifying information
> > >> about Linux Security Modules (LSMs). At inception this contains
> > >> the name of the module and an identifier associated with the
> > >> security module. Change the security_add_hooks() interface to
> > >> use this structure. Change the individual modules to maintain
> > >> their own struct lsm_id and pass it to security_add_hooks().
> > >>
> > >> The values are for LSM identifiers are defined in a new UAPI
> > >> header file linux/lsm.h. Each existing LSM has been updated to
> > >> include it's LSMID in the lsm_id.
> > >>
> > >> The LSM ID values are sequential, with the oldest module
> > >> LSM_ID_CAPABILITY being the lowest value and the existing modules
> > >> numbered in the order they were included in the main line kernel.
> > >> This is an arbitrary convention for assigning the values, but
> > >> none better presents itself. The value 0 is defined as being invalid.
> > >> The values 1-99 are reserved for any special case uses which may
> > >> arise in the future.
> > >
> > > What would be a "special case" that deserves a lower number?
> >
> > I don't see any meaningful use case for these reserved numbers either.
> > If there are some, let's put them now, otherwise we should start with 1.
> > Is it inspired by an existing UAPI?
> > Reserving 0 as invalid is good though.
> 
> I haven't finished reviewing this latest patchset, but I wanted to
> comment on this quickly while I had a moment in front of a keyboard
> ... I did explain my desire and reasoning for this in a previous
> revision of this patchset and I still believe the
> reserved-for-potential-future-use to be a valid reason so I'm going to
> ask for this to remain.

Then that reasoning and explaination needs to be here in the changelog
so that we understand and have a chance to agree/disagree with that.
Otherwise we, and everyone else, are left to just be confused.

thanks,

greg k-h